GPS software solution

I bought a receiver, but I need some software now. What is the best bang for the buck? I have seen some packages in the $100+ dollar range, but that seems a lot for the software only considering the low cost of complete nav systems these days!

I found the Google Maps on the Centro to be neat for free. I haven't actually tested it in the car but it does give you turn by turn, without the GPS. I guess if you miss the turn you're screwed but who here does that?